Relocation of Schistosoma mansoni in the lungs and resistance to reinfection in Rattus rattus.

The localization of adult Schistosoma mansoni originating from Guadeloupe (West Indies) was analysed in the natural host Rattus rattus in experimental and natural infections. A transfer of schistosomes from the porto-mesenteric system to the lungs occurs between the 4th and the 20th weeks post-infection, with a peak between 4 and 8 weeks; it should be noted that the worms start laying eggs at 4 weeks post-infection. In both experimentally and naturally infected R. rattus the relocation of schistosomes in the lungs is correlated with the total worm burden. Between 6 and 12 weeks post-infection some adult worms and numerous eggs are trapped in the liver. A high mortality in the worm population coincides with the migration of the parasites from the porto-mesenteric veins to the lungs. In re-infected R. rattus a relationship appears between the presence of schistosomes in the lungs and resistance to reinfection. It is concluded that, as already postulated previously in mice, resistance to re-infection in the natural host R. rattus is at least partly correlated with the hepatic pathology caused by the schistosomes of the primary infection.